nedmalloc: avoid new compile error

GCC v12.x complains thusly:

compat/nedmalloc/nedmalloc.c: In function 'DestroyCaches':
compat/nedmalloc/nedmalloc.c:326:12: error: the comparison will always
                              evaluate as 'true' for the address of 'caches'
                              will never be NULL [-Werror=address]
  326 |         if(p->caches)
      |            ^
compat/nedmalloc/nedmalloc.c:196:22: note: 'caches' declared here
  196 |         threadcache *caches[THREADCACHEMAXCACHES];
      |                      ^~~~~~

... and it is correct, of course.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/nedmalloc/nedmalloc.c

@@ -323,7 +323,6 @@ static NOINLINE void RemoveCacheEntries(nedpool *p, threadcache *tc, unsigned in
 }
 static void DestroyCaches(nedpool *p) THROWSPEC
 {
-	if(p->caches)
 	{
 		threadcache *tc;
 		int n;